Enabling half-duplex operation

ABSTRACT

Half-duplex (HD) operations enable low cost implementations of LTE terminals. Traditionally, HD operations may be linked to a particular frequency band which may not allow a mix of full-duplex (FD) and HD terminals in the same frequency band. Therefore, certain aspects of the present disclosure provide techniques for enabling coexistence, in a given frequency band, of HD and FD terminals, by introducing frequency bands designated for HD operation and overlapping existing frequency bands designated for FD operation.

CROSS-REFERENCE TO RELATED APPLICATION

The present application for patent is a Divisional application ofapplication Ser. No. 13/550,834, filed Jul. 17, 2012, which claimspriority to U.S. Provisional Application Ser. No. 61/508,879, filed Jul.18, 2011, and U.S. Provisional Application Ser. No. 61/511,815, filedJul. 26, 2011, all of which are expressly incorporated by referenceherein in their entirety.

BACKGROUND

I. Field

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to techniques for enablingcoexistence, in a given frequency band, of half-duplex (HD) andfull-duplex (FD) terminals.

II. Background

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE)/LTE-Advanced systems andorthogonal frequency division multiple access (OFDMA) systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-input single-output, multiple-inputsingle-output or a multiple-input multiple-output (MIMO) system.

SUMMARY

Certain aspects of the present disclosure provide a method for enablingcoexistence of half-duplex (HD) operations and full-duplex (FD)operations in a same carrier. The method generally includes assigning afirst frequency band for HD operations, and assigning a second frequencyband for FD operations, wherein the first frequency band for HDoperations overlaps the second frequency band for FD operations.

Certain aspects of the present disclosure provide an apparatus forenabling coexistence of HD operations and FD operations in a samecarrier. The apparatus generally includes means for assigning a firstfrequency band for HD operations and means for assigning a secondfrequency band for FD operations, wherein the first frequency band forHD operations overlaps the second frequency band for FD operations.

Certain aspects of the present disclosure provide an apparatus forenabling coexistence of HD operations and FD operations in a samecarrier. The apparatus generally includes at least one processor and amemory coupled to the at least one processor. The at least one processoris generally configured to assign a first frequency band for HDoperations and assign a second frequency band for FD operations, whereinthe first frequency band for HD operations overlaps the second frequencyband for FD operations.

Certain aspects of the present disclosure provide a computer-programproduct for enabling coexistence of HD operations and FD operations in asame carrier. The computer-program product generally includes acomputer-readable medium having code for assigning a first frequencyband for HD operations and assigning a second frequency band for FDoperations, wherein the first frequency band for HD operations overlapsthe second frequency band for FD operations.

Certain aspects of the present disclosure provide a method for enablingcoexistence of HD operations and FD operations in a same carrier. Themethod generally includes receiving an indication of a first frequencyband for HD operations and a second frequency band for FD operations,wherein the first frequency band overlaps the second frequency band, anddetermining whether to operate in the first or second frequency bandbased on a user equipment (UE) type.

Certain aspects of the present disclosure provide an apparatus forenabling coexistence of HD operations and FD operations in a samecarrier. The apparatus generally includes means for receiving anindication of a first frequency band for HD operations and a secondfrequency band for FD operations, wherein the first frequency bandoverlaps the second frequency band and means for determining whether tooperate in the first or second frequency band based on a UE type.

Certain aspects of the present disclosure provide an apparatus forenabling coexistence of HD operations and FD operations in a samecarrier. The apparatus generally includes at least one processor and amemory coupled to the at least one processor. The at least one processoris generally configured to receive an indication of a first frequencyband for HD operations and a second frequency band for FD operations,wherein the first frequency band overlaps the second frequency band anddetermine whether to operate in the first or second frequency band basedon a UE type.

Certain aspects of the present disclosure provide a computer-programproduct for enabling coexistence of HD operations and FD operations in asame carrier. The computer-program product generally includes acomputer-readable medium having code for receiving an indication of afirst frequency band for HD operations and a second frequency band forFD operations, wherein the first frequency band overlaps the secondfrequency band and determining whether to operate in the first or secondfrequency band based on a UE type.

Certain aspects of the present disclosure provide a method for wirelesscommunications. The method generally includes determining an uplinktransmission overlaps with a downlink transmission in a subframe, andcontrolling transmissions with one or more HD UEs such that only one ofthe uplink transmission or the downlink transmission is performed in thesubframe with one or more of the UEs.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means fordetermining an uplink transmission overlaps with a downlink transmissionin a subframe and means for controlling transmissions with one or moreHD UEs such that only one of the uplink transmission or the downlinktransmission is performed in the subframe with one or more of the UEs.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes at least oneprocessor and a memory coupled to the at least one processor. The atleast one processor is generally configured to determine an uplinktransmission overlaps with a downlink transmission in a subframe andcontrol transmissions with one or more HD UEs such that only one of theuplink transmission or the downlink transmission is performed in thesubframe with one or more of the UEs.

Certain aspects of the present disclosure provide a computer-programproduct for wireless communications. The computer-program productgenerally includes a computer-readable medium having code fordetermining an uplink transmission overlaps with a downlink transmissionin a subframe and controlling transmissions with one or more half-duplexHD UEs such that only one of the uplink transmission or the downlinktransmission is performed in the subframe with one or more of the UEs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram conceptually illustrating an example of awireless communication network, in accordance with certain aspects ofthe present disclosure.

FIG. 2 shows a block diagram conceptually illustrating an example of abase station in communication with a user equipment (UE) in a wirelesscommunications network, in accordance with certain aspects of thepresent disclosure.

FIG. 3 is a block diagram conceptually illustrating an example of aframe structure in a wireless communications network, in accordance withcertain aspects of the present disclosure.

FIG. 4 illustrates two exemplary subframe formats for the downlink, inaccordance with certain aspects of the present disclosure.

FIG. 5 illustrates an example decision tree for LTE half-duplex (HD)operations that may be performed by a UE, according to certain aspectsof the present disclosure.

FIG. 6 illustrates an example system with an access point and an accessterminal, capable of broadcasting a network indication of a capabilityfor supporting FD and HD operations on a frequency band, in accordancewith certain aspects of the present disclosure.

FIG. 7 illustrates example operations for enabling coexistence of HDoperations and FD operations in a same carrier, in accordance withcertain aspects of the present disclosure.

FIG. 8 illustrates example operations, in accordance with certainaspects of the present disclosure.

FIGS. 9A-B illustrate an example of enabling coexistence of HDoperations and FD operations in a same carrier, in accordance withcertain aspects of the present disclosure.

FIG. 10 illustrates example operations for controlling transmissionswith one or more HD UEs, in accordance with certain aspects of thepresent disclosure.

FIGS. 11-12 illustrate the impact of DL assignments and UL grants in aHD operation, according to certain aspects of the present disclosure.

DETAILED DESCRIPTION

Half-duplex (HD) operations enable low cost implementations of LTEterminals. Traditionally, HD operations may be linked to a particularfrequency band which may not allow a mix of full-duplex (FD) and HDterminals in the same frequency band. Therefore, certain aspects of thepresent disclosure provide techniques for enabling coexistence, in agiven frequency band, of HD and FD terminals, by introducing frequencybands designated for HD operation and overlapping existing frequencybands designated for FD operation.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asuniversal terrestrial radio access (UTRA), cdma2000, etc. UTRA includeswideband CDMA (WCDMA), time division synchronous CDMA (TD-SCDMA), andother variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asglobal system for mobile communications (GSM). An OFDMA network mayimplement a radio technology such as evolved UTRA (E-UTRA), ultra mobilebroadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM®, etc. UTRA and E-UTRA are part of universal mobiletelecommunication system (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A), in both frequency division duplex (FDD) and timedivision duplex (TDD), are new releases of UMTS that use E-UTRA, whichemploys OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA,UMTS, LTE, LTE-A and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the wireless networks and radio technologies mentioned above aswell as other wireless networks and radio technologies. For clarity,certain aspects of the techniques are described below forLTE/LTE-Advanced, and LTE/LTE-Advanced terminology is used in much ofthe description below.

FIG. 1 shows a wireless communication network 100, which may be an LTEnetwork or some other wireless network. Wireless network 100 may includea number of evolved Node Bs (eNBs) 110 and other network entities. AneNB is an entity that communicates with user equipments (UEs) and mayalso be referred to as a base station, a Node B, an access point, etc.Each eNB may provide communication coverage for a particular geographicarea. In 3GPP, the term “cell” can refer to a coverage area of an eNBand/or an eNB subsystem serving this coverage area, depending on thecontext in which the term is used.

An eNB may provide communication coverage for a macro cell, a pico cell,a femto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a closed subscriber group (CSG)). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a pico cell may be referred to asa pico eNB. An eNB for a femto cell may be referred to as a femto eNB ora home eNB (HeNB). In the example shown in FIG. 1, an eNB 110 a may be amacro eNB for a macro cell 102 a, an eNB 110 b may be a pico eNB for apico cell 102 b, and an eNB 110 c may be a femto eNB for a femto cell102 c. An eNB may support one or multiple (e.g., three) cells. The terms“eNB”, “base station” and “cell” may be used interchangeably herein.

Wireless network 100 may also include relay stations. A relay station isan entity that can receive a transmission of data from an upstreamstation (e.g., an eNB or a UE) and send a transmission of the data to adownstream station (e.g., a UE or an eNB). A relay station may also be aUE that can relay transmissions for other UEs. In the example shown inFIG. 1, a relay station 110 d may communicate with macro eNB 110 a and aUE 120 d in order to facilitate communication between eNB 110 a and UE120 d. A relay station may also be referred to as a relay eNB, a relaybase station, a relay, etc.

Wireless network 100 may be a heterogeneous network that includes eNBsof different types, e.g., macro eNBs, pico eNBs, femto eNBs, relay eNBs,etc. These different types of eNBs may have different transmit powerlevels, different coverage areas, and different impact on interferencein wireless network 100. For example, macro eNBs may have a hightransmit power level (e.g., 5 to 40 Watts) whereas pico eNBs, femtoeNBs, and relay eNBs may have lower transmit power levels (e.g., 0.1 to2 Watts).

A network controller 130 may couple to a set of eNBs and may providecoordination and control for these eNBs. Network controller 130 maycommunicate with the eNBs via a backhaul. The eNBs may also communicatewith one another, e.g., directly or indirectly via a wireless orwireline backhaul.

UEs 120 may be dispersed throughout wireless network 100, and each UEmay be stationary or mobile. A UE may also be referred to as an accessterminal, a terminal, a mobile station, a subscriber unit, a station,etc. A UE may be a cellular phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet, a smart phone, a netbook, a smartbook, etc.

FIG. 2 shows a block diagram of a design of base station/eNB 110 and UE120, which may be one of the base stations/eNBs and one of the UEs inFIG. 1. Base station 110 may be equipped with T antennas 234 a through234 t, and UE 120 may be equipped with R antennas 252 a through 252 r,where in general T≧1 and R≧1.

At base station 110, a transmit processor 220 may receive data from adata source 212 for one or more UEs, select one or more modulation andcoding schemes (MCS) for each UE based on CQIs received from the UE,process (e.g., encode and modulate) the data for each UE based on theMCS(s) selected for the UE, and provide data symbols for all UEs.Transmit processor 220 may also process system information (e.g., forSRPI, etc.) and control information (e.g., CQI requests, grants, upperlayer signaling, etc.) and provide overhead symbols and control symbols.Processor 220 may also generate reference symbols for reference signals(e.g., the CRS) and synchronization signals (e.g., the PSS and SSS). Atransmit (TX) multiple-input multiple-output (MIMO) processor 230 mayperform spatial processing (e.g., precoding) on the data symbols, thecontrol symbols, the overhead symbols, and/or the reference symbols, ifapplicable, and may provide T output symbol streams to T modulators(MODs) 232 a through 232 t. Each modulator 232 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator 232 may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. T downlink signals from modulators 232 a through 232 tmay be transmitted via T antennas 234 a through 234 t, respectively.

At UE 120, antennas 252 a through 252 r may receive the downlink signalsfrom base station 110 and/or other base stations and may providereceived signals to demodulators (DEMODs) 254 a through 254 r,respectively. Each demodulator 254 may condition (e.g., filter, amplify,downconvert, and digitize) its received signal to obtain input samples.Each demodulator 254 may further process the input samples (e.g., forOFDM, etc.) to obtain received symbols. A MIMO detector 256 may obtainreceived symbols from all R demodulators 254 a through 254 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 258 may process (e.g., demodulateand decode) the detected symbols, provide decoded data for UE 120 to adata sink 260, and provide decoded control information and systeminformation to a controller/processor 280. A channel processor maydetermine RSRP, RSSI, RSRQ, CQI, etc.

On the uplink, at UE 120, a transmit processor 264 may receive andprocess data from a data source 262 and control information (e.g., forreports comprising RSRP, RSSI, RSRQ, CQI, etc.) fromcontroller/processor 280. Processor 264 may also generate referencesymbols for one or more reference signals. The symbols from transmitprocessor 264 may be precoded by a TX MIMO processor 266 if applicable,further processed by modulators 254 a through 254 r (e.g., for SC-FDM,OFDM, etc.), and transmitted to base station 110. At base station 110,the uplink signals from UE 120 and other UEs may be received by antennas234, processed by demodulators 232, detected by a MIMO detector 236 ifapplicable, and further processed by a receive processor 238 to obtaindecoded data and control information sent by UE 120. Processor 238 mayprovide the decoded data to a data sink 239 and the decoded controlinformation to controller/processor 240. Base station 110 may includecommunication unit 244 and communicate to network controller 130 viacommunication unit 244. Network controller 130 may include communicationunit 294, controller/processor 290, and memory 292.

Controllers/processors 240 and 280 may direct the operation at basestation 110 and UE 120, respectively. Processor 240 and/or otherprocessors and modules at base station 110, and/or processor 280 and/orother processors and modules at UE 120, may perform or direct processesfor the techniques described herein. Memories 242 and 282 may store dataand program codes for base station 110 and UE 120, respectively. Ascheduler 246 may schedule UEs for data transmission on the downlinkand/or uplink.

As will be described in further detail below, when transmitting data tothe UE 120, the base station 110 may be configured to determine abundling size based at least in part on a data allocation size andprecode data in bundled contiguous resource blocks of the determinedbundling size, wherein resource blocks in each bundle may be precodedwith a common precoding matrix. That is, reference signals such as UE-RSand/or data in the resource blocks may be precoded using the sameprecoder. The power level used for the UE-RS in each RB of the bundledRBs may also be the same.

The UE 120 may be configured to perform complementary processing todecode data transmitted from the base station 110. For example, the UE120 may be configured to determine a bundling size based on a dataallocation size of received data transmitted from a base station inbundles of contiguous resource blocks (RBs), wherein at least onereference signal in resource blocks in each bundle are precoded with acommon precoding matrix, estimate at least one precoded channel based onthe determined bundling size and one or more reference signals (RSs)transmitted from the base station, and decode the received bundles usingthe estimated precoded channel.

FIG. 3 shows an exemplary frame structure 300 for FDD in LTE. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 milliseconds (ms)) and may bepartitioned into 10 subframes with indices of 0 through 9. Each subframemay include two slots. Each radio frame may thus include 20 slots withindices of 0 through 19. Each slot may include L symbol periods, e.g.,seven symbol periods for a normal cyclic prefix (as shown in FIG. 2) orsix symbol periods for an extended cyclic prefix. The 2L symbol periodsin each subframe may be assigned indices of 0 through 2L−1.

In LTE, an eNB may transmit a primary synchronization signal (PSS) and asecondary synchronization signal (SSS) on the downlink in the center1.08 MHz of the system bandwidth for each cell supported by the eNB. ThePSS and SSS may be transmitted in symbol periods 6 and 5, respectively,in subframes 0 and 5 of each radio frame with the normal cyclic prefix,as shown in FIG. 3. The PSS and SSS may be used by UEs for cell searchand acquisition. The eNB may transmit a cell-specific reference signal(CRS) across the system bandwidth for each cell supported by the eNB.The CRS may be transmitted in certain symbol periods of each subframeand may be used by the UEs to perform channel estimation, channelquality measurement, and/or other functions. The eNB may also transmit aphysical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 ofcertain radio frames. The PBCH may carry some system information. TheeNB may transmit other system information such as system informationblocks (SIBs) on a physical downlink shared channel (PDSCH) in certainsubframes. The eNB may transmit control information/data on a physicaldownlink control channel (PDCCH) in the first B symbol periods of asubframe, where B may be configurable for each subframe. The eNB maytransmit traffic data and/or other data on the PDSCH in the remainingsymbol periods of each subframe.

FIG. 4 shows two exemplary subframe formats 410 and 420 for the downlinkwith the normal cyclic prefix. The available time frequency resourcesfor the downlink may be partitioned into resource blocks. Each resourceblock may cover 12 subcarriers in one slot and may include a number ofresource elements. Each resource element may cover one subcarrier in onesymbol period and may be used to send one modulation symbol, which maybe a real or complex value.

Subframe format 410 may be used for an eNB equipped with two antennas. ACRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7and 11. A reference signal is a signal that is known a priori by atransmitter and a receiver and may also be referred to as pilot. A CRSis a reference signal that is specific for a cell, e.g., generated basedon a cell identity (ID). In FIG. 4, for a given resource element withlabel R_(a), a modulation symbol may be transmitted on that resourceelement from antenna a, and no modulation symbols may be transmitted onthat resource element from other antennas. Subframe format 420 may beused for an eNB equipped with four antennas. A CRS may be transmittedfrom antennas 0 and 1 in symbol periods 0, 4, 7 and 11 and from antennas2 and 3 in symbol periods 1 and 8. For both subframe formats 410 and420, a CRS may be transmitted on evenly spaced subcarriers, which may bedetermined based on cell ID. Different eNBs may transmit their CRSs onthe same or different subcarriers, depending on their cell IDs. For bothsubframe formats 410 and 420, resource elements not used for the CRS maybe used to transmit data (e.g., traffic data, control data, and/or otherdata).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP TS 36.211,entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); PhysicalChannels and Modulation,” which is publicly available.

An interlace structure may be used for each of the downlink and uplinkfor FDD in LTE. For example, Q interlaces with indices of 0 through Q−1may be defined, where Q may be equal to 4, 6, 8, 10, or some othervalue. Each interlace may include subframes that are spaced apart by Qframes. In particular, interlace q may include subframes q, q+Q, q+2Q,etc., where qε{0, Q−1}.

The wireless network may support hybrid automatic retransmission request(HARQ) for data transmission on the downlink and uplink. For HARQ, atransmitter (e.g., an eNB) may send one or more transmissions of apacket until the packet is decoded correctly by a receiver (e.g., a UE)or some other termination condition is encountered. For synchronousHARQ, all transmissions of the packet may be sent in subframes of asingle interlace. For asynchronous HARQ, each transmission of the packetmay be sent in any subframe.

A UE may be located within the coverage of multiple eNBs. One of theseeNBs may be selected to serve the UE. The serving eNB may be selectedbased on various criteria such as received signal strength, receivedsignal quality, pathloss, etc. Received signal quality may be quantifiedby a signal-to-noise-and-interference ratio (SINR), or a referencesignal received quality (RSRQ), or some other metric. The UE may operatein a dominant interference scenario in which the UE may observe highinterference from one or more interfering eNBs.

Enabling Half-Duplex Operation

LTE Re1-8 supports a frame structure for frequency division duplex (FDD)(e.g., FIG. 3) and a frame structure for time division duplex (TDD). Theframe structure for FDD may provide support for full-duplex (FD) andhalf-duplex (HD) operation modes. While for FD operations there may beno restrictions about when a user equipment (UE) may transmit orreceive, for HD operations, the UE may only transmit or receive at agiven point in time. HD operations were introduced in Re1-8 of LTE toenable low cost implementations of LTE terminals comparable to those ofGSM (e.g., an FDD HD system). The primary cost savings from HDoperations may stem from the absence of a duplexer. Even though HDoperations provide cost-savings at the terminal side, the infrastructureneeds to support the operation mode.

For HD FDD operations, a guard period may be created by the UE by notreceiving the last part of a downlink subframe immediately preceding anuplink subframe from the same UE (e.g., non-zero transition time). ForHD operations, the UL transmission timing may be aligned by notreceiving the last part of the downlink subframe. For some embodiments,an eNB may use this knowledge to adjust the DL transmission ratewhenever the eNB schedules the HD UE for the UL immediately following aDL transmission.

Traditionally, HD operations may be linked to a particular frequencyband which may not make possible the mix of FD and HD terminals in thesame frequency band. Therefore, HD operation may only be supported infrequency bands entirely dedicated to this operation type. In otherwords, one cell may only support transmission on one band. Therefore,there may be no perceived need for the network indication of the HDsupport as it is linked to the frequency band.

FIG. 5 illustrates an example decision tree for LTE HD operations thatmay be performed by a UE, according to certain aspects of the presentdisclosure. The HD operations in LTE may be regarded as mainly animplementation issue not requiring air-interface specifications. At 502,at the beginning of every subframe (assuming a zero transition time fromtransmit to receive or vice versa), the UE may determine whether or notit has to transmit any channel or signal in the subframe. With anon-zero transition time, this determination may be made before the endof the previous subframe. At 504, if the UE determines it has totransmit something, the UE may use this subframe for transmissionpurposes, and an eNB may not transmit to the UE. Otherwise, at 506, theUE may use this subframe for reception (i.e., the eNB may transmit tothe UE). As illustrated in FIG. 5, the UE may prioritize itstransmissions before any reception. LTE HD operation may require the UEand the eNB to continuously check the need or expectation for the UE totransmit, to determine whether the UE will be able to receive in a givensubframe. Since there is not a fixed structure in the time-domainwaveform for HD operation support, LTE may support concurrent support ofFD and HD devices.

The eNB (e.g., scheduler) may know when the UE has to transmit somethingin a given subframe and, therefore, the eNB may be expected to use thisinformation to determine when to schedule UE transmissions andreceptions. Since the UE transmissions may not be affected by the HDoperation, there may be no need to specify any special UE behavior fromthe UE transmitter standpoint (e.g., regular UL operation). For the DL,however, not all the subframes may be available for the UE to receive orfor the eNB to transmit to the given UE. However, the eNB behavior maynot need to be specified.

For some embodiments, for concurrent operation of FD and HD in the samefrequency band, a new frequency band (e.g., new band number) may becreated for HD operations, overlapping an existing frequency band for FDoperations, with corresponding signaling of the two bands from thenetwork. For certain aspects, the new frequency band for HD operationsmay completely overlap the existing frequency band for FD operations. Inother words, a particular frequency band may be overloaded with an FDdesignation and a HD designation. For certain aspects, the new frequencyband for HD operations may have a narrower bandwidth than the existingfrequency band for FD operations, and the two bands may overlap for thenarrower bandwidth. Therefore, FD UEs may effectively operate in the FDDFD band and HD UEs may effectively operate in the FDD HD band. Forcertain aspects, the eNB may include two band numbers in overheadmessages, allowing for simultaneous operation of FD and HD UEs. For someembodiments, an indication of HD support may be added to the networksignaling.

FIG. 6 illustrates an example system 600 with an access point 610 and anaccess terminal 620 (e.g., HD UE), capable of broadcasting a networkindication of a capability for supporting FD and HD operations on afrequency band, in accordance with certain aspects of the presentdisclosure. As illustrated, the access point 610 may include a messagegeneration module 614 for generating an overhead message for indicatinga band number for HD operations and a band number for FD operations. Theoverhead message may be transmitted in a downlink subframe, via atransmitter module 612, to the HD UE 620.

The HD UE 620 may receive the overhead message via a receiver module 626and determine the frequency band for HD operations via a messageprocessing module 624. After receiving and processing the overheadmessage, the HD UE 620 may construct and transmit an acknowledgmentaccording to the HD band number, via a transmitter module 622, to theaccess point 610 in an uplink subframe. The access point 610 may receivethe acknowledgment via a receiver module 616.

Without the network capability to convey to the UEs that a network doesnot support HD operation in a given band, a HD UE may be camping in aparticular frequency band in LTE idle mode without anyproblem/restriction and without realizing that HD operation is notsupported by the network. For example, a HD UE may roam to a place wherea particular frequency band is not used in HD mode but in FD mode. Insuch a case, the network may realize the HD support for this bandoperation from the reported UE capability from the UE and may baroperation in that frequency band to that terminal. The HD UE may realizethis mismatch only when trying to go to LTE connected mode. Therefore,according to certain aspects of the present disclosure, the networkcapability may be broadcasted.

FIG. 7 illustrates example operations 700 for enabling coexistence of HDoperations and FD operations in a same carrier, in accordance withcertain aspects of the present disclosure. The operations 700 may beperformed, for example, by an eNB. At 702, the eNB may assign a firstfrequency band for HD operations.

At 704, the eNB may assign a second frequency band for FD operations,wherein the first frequency band for HD operations overlaps the secondfrequency band for FD operations. For some embodiments, the frequencyband for HD operations may have a first band number and the secondfrequency band for FD operations may have a second band number, whereinthe first and second band numbers may be transmitted in an overheadmessage. The first and second band numbers may allow for simultaneousoperation of FD UEs and HD UEs. For certain aspects, the eNB mayreceive, from a UE, an indication of whether the UE supports HDoperations or FD operations and, based on the indication, the eNB mayschedule the UE in the first or second band.

For certain aspects, the first frequency band for HD operations maycompletely overlap the second frequency band for FD operations, suchthat assignment of the first and second frequency bands generallyincludes assigning a frequency band with the first band number and thesecond band number. For certain aspects, the first frequency band for HDoperations may have a narrower bandwidth than the second frequency bandfor FD operations. For some embodiments, the eNB may broadcast a networkindication in the first frequency band, wherein the broadcast mayindicate a capability for supporting the HD operations on the frequencyband.

For certain aspects, the eNB may broadcast a network indication in thesecond frequency band for FD operations, wherein the broadcast indicateswhether there is support for HD operations. If the broadcast indicatesthere is no support for HD operations, the eNB may deny access to a UEthat only supports HD operations.

FIG. 8 illustrates example operations 800, in accordance with certainaspects of the present disclosure. The operations 800 may be performed,for example, by a UE. At 802, the UE may receive an indication of afirst frequency band for HD operations and a second frequency band forFD operations, wherein the first frequency band overlaps the secondfrequency band. For certain aspects, the UE may receive a first bandnumber corresponding to the first frequency band and a second bandnumber corresponding to the second frequency band, wherein the first andsecond band numbers may be received in an overhead message.

At 804, the UE may determine whether to operate in the first or secondfrequency band based on a UE type (e.g., whether the UE is a FD UE or aHD UE). Therefore, the first and second band numbers may allow forsimultaneous operation of FD UEs and HD UEs. For certain aspects, the UEmay receive a network indication (e.g., in the second frequency band forFD operations) indicating whether there is network support for HDoperations. In other words, if an HD UE does not receive such a networkindication, the HD UE may perform network acquisition operations withanother base station that does support HD operations.

FIGS. 9A-B illustrate an example of enabling coexistence of HDoperations and FD operations in a same carrier, in accordance withcertain aspects of the present disclosure. FIG. 9A illustrates afrequency band 902 for FD operations with a first band number. FIG. 9Billustrates a frequency band 904 created for HD operations, overlappingthe existing frequency band 902 for FD operations. For certain aspects,the frequency band 904 for HD operations may completely overlap or havea narrower bandwidth than the frequency band 902 for FD operations, asdescribed above. The frequency band 904 for HD operations may have asecond band number, as illustrated. As described above, the first andsecond band numbers may be transmitted in an overhead message, which mayallow for simultaneous operation of FD UEs and HD UEs.

For a UE that is in LTE idle state, the UE is, by definition, onlyreceiving information from the network, e.g., system information andpages. Since there may be no UE transmissions, the HD UE may not haveany limitations and may receive network transmissions in every subframewithout restrictions.

However, for a UE that is in LTE connected state, whether the UEreceives a page or triggers an access on itself, it may start with arandom access procedure. For example, the UE may transmit a physicalrandom access channel (PRACH) on a designated subframe (e.g., message 1transmission from the UE). After sending message 1, the UE may not haveto transmit anything until it receives message 2 from the network (e.g.,message 2 reception at the UE). Therefore, there may be no restrictionsin receiving message 2. Once message 2 is received at the UE, the UE mayneed to decode the message to determine the resources for message 3.From the reception of message 2 to the transmission of message 3 (e.g.,message 3 transmission from the UE), the UE may not be expected toreceive anything nor may need to transmit anything. After sendingmessage 3, the UE may not have to transmit anything until it receivesmessage 4 from the network (e.g., message 4 reception at the UE).Therefore, there may be no restrictions in receiving message 4 either.Once message 4 is received at the UE, the UE may need to decode themessage to determine the allocated data resources. The network mayconfigure channel quality indicator (CQI) reports, scheduling request(SR) resources, and sounding reference signal (SRS) transmissions forthe UE.

For certain aspects, system information changes (e.g., signaled by wayof PRNTI (paging-radio network temporary identifier)) may occur when thenetwork has knowledge that HD terminals are not transmitting and,therefore, are listening. However, the system information may changewhile the UE is transmitting a message (e.g., message 1 or 3). For someembodiments, in order to minimize missing the system informationchanges, the network may page multiple times. For example, the pagingsubframes may be subframe 9 only, subframes 4 and 9, or subframes 0, 4,5, and 9. For some embodiments, dedicated signaling for HD UEs may beused (e.g., HD-RNTI), to address all or a group of HD UEs for signalingof, e.g., a change of system information.

While in the LTE connected state, examples of channels and signals thatmay be transmitted include, but are not limited to, a physical uplinkshared channel (PUSCH), a physical uplink control channel schedulingrequest (PUCCH-SR), PUCCH-ACK, PUCCH-CQI, SRS, a periodic CQI andaperiodic SRS, and PRACH for downlink data arrival/resynchronizationbetween the eNB and the UE (e.g., connected mode RACH). PUSCH may be theresult of an UL grant four subframes before, an unscheduledre-transmission (e.g., non-positive physical hybrid ARQ indicatorchannel (PHICH) four subframes before), or a semi-persistent scheduling(SPS) configuration. PUCCH-SR, PUCCH-CQI, and SRS may be the result of ahigher layer configuration by the network. PUCCH-ACK may be the resultof DL transmissions four subframes before. Given that a SRS may betransmitted in the last SC-FDMA symbol of the subframe, the UE maychoose to try to decode the DL subframe if nothing else is to betransmitted in that subframe (e.g., the eNB may determine theallocation/MCS to accommodate the loss of the last symbol and the guardtime necessary to switch from reception to transmission). A periodic CQIand aperiodic SRS may be configured by the network.

While in the LTE connected state, examples of channels that may berelevant for reception generally include a PHICH (e.g., if there was aPUSCH transmission four subframes before), a physical control formatindicator channel (PCFICH), a physical downlink control channel (PDCCH),and a physical downlink shared channel (PDSCH).

For some embodiments, the system information may change and UEs may beinformed by paging. Since there are specific subframes for paging, thesesubframes may be available for the UE to listen. However, given that thepaging subframes may have a periodicity of 10 ms and HARQ operation mayhave a periodicity of 8 ms, there may be subframes where HD UEs may notbe able to receive pages or may not be able to transmit. Therefore, UEbehavior may need to be defined to prioritize transmissions orreceptions, as will be discussed further herein.

FIG. 10 illustrates example operations 1000 for controllingtransmissions with one or more HD UEs, in accordance with certainaspects of the present disclosure. The operations 1000 may be performed,for example, by an eNB. At 1002, the eNB may determine that an uplinktransmission overlaps with a downlink transmission in a subframe. Asexamples, the downlink transmission generally includes a paging messageindicating a system information change, and the uplink transmissiongenerally includes an uplink hybrid automatic retransmission request(HARQ) operation. For certain aspects, determination of the overlapgenerally includes comparing CQI report differences in CSI reportingsubsets from the one or more HD UEs, and determining incompatibledownlink/uplink allocations between the one or more HD UEs.

At 1004, the eNB may control transmissions with the one or more HD UEssuch that only one of the uplink transmission or the downlinktransmission is performed in the subframe with one or more of the UE.For some embodiments, controlling generally includes suspending theother one of the uplink transmission or the downlink transmission fortransmission in a later subframe. For some embodiments, controllinggenerally includes prioritizing the uplink transmission or the downlinktransmission over the other.

The transmissions of CQI and SR may be configured by higher layers withperiodicities being multiples or submultiples of 10 ms (e.g., 2 ms or 5ms). These transmissions may condition the setting of subframes to “UL”and may be chosen to avoid the paging subframes, which also roll-overwith 10 ms periodicity. Therefore, the transmission of CQI and SR maynot interfere in any way with the reception of paging subframes as theycan be properly separated without sliding effects (discussed below). TheUL subframes may be used for PUSCH transmissions, with the understandingthat the corresponding UL grant (e.g., four subframes before) may occurin a “DL” subframe.

FIG. 11 illustrates the impact of DL assignments and UL grants in a HDoperation, according to certain aspects of the present disclosure. Asillustrated, the timeline associated with UL assignments 1104 may belinked to fixed 4 ms intervals (e.g., from grant, to initialtransmission, to reception of DL ACKs, and to retransmissions). However,due to the time-asynchronicity of PDSCH, the timeline associated with DLassignments 1102 may not be linked to fixed 4 ms intervals. For example,the DL retransmission that takes place at 1106 may occur after 5 ms fromthe PUCCH ACK 1108.

For some embodiments, if the DL retransmissions are chosen to follow thesame timeline as the UL, a perfect split of UL/DL resources may beattained, as illustrated in FIG. 12 (e.g., for every four subframes, theUE may switch between UL and DL resources).

Given that there are two timelines (e.g., HARQ operation for ULretransmissions over an 8 ms basis and paging subframes for DL receptionover a 10 ms basis), the two timelines may slide over each other. Forsome embodiments, the eNB may suspend retransmissions that would fallinto paging subframes by properly sending a NACK on the preceding PHICH.For some embodiments, the eNB may prioritize at least one ofretransmitting PUSCH and receiving pages over the other.

For certain aspects, PUSCH may be scheduled in subframes where other ULPHY channels are transmitted. For example, PUSCH may be scheduled in asubframe where PUCCH or SRS are transmitted, since that subframe may bean UL subframe. HD operation inherently utilizes only half of the systemresource per UE compared to FD operation. Therefore, an eNB mayefficiently utilize frequency time resources by balancing differentusers.

Due to reduced UL-DL interference reduction in HD UEs, DL receiverperformance of a UE may be compromised when another UE is transmittingin close proximity. Due to load balancing, the eNB may offset the DL andUL subframes between different UEs, which can lead to coexistenceproblems. For certain aspects, the eNB may have algorithms that candiscover such issues and make appropriate scheduling changes. Forexample, the eNB may use different scheduling sets and may configure theUEs with different CSI reporting subsets. Then by comparing the CQIreport difference in the different CSI reporting subsets from a givenUE, the eNB may infer the proximity of another UE with an incompatibleDL/UL allocation and may change the allocation of the target UE.

Proper radio resource management (RRM) functionality may require theavailability of a sufficient number of DL subframes for measurements. Itmay or may not be needed to designate a subset of subframes that areavailable for DL measurements for RRM purposes. In lack of a designatedsubset, the eNB may make subframes available dynamically by scheduling.Due to the need for PDCCH/PHICH operation to support the UL, the ULsubframe ratio relative to the total may not be greater than 50%. Thisalready ensures that there may be a sufficient number of DL subframesavailable for measurements. However, it should also be assured thatthere is opportunity to measure subframes containing PSS/SSS of neighborcells. This may be accomplished in time synchronous networks. However,in asynchronous networks, the measurement opportunities may be createdin a diversified way so that the UE can measure cells with arbitrarytiming offsets relative to the current serving cell.

In order to properly support eNB scheduling operations, the expected UEswitch times may need to be accounted for. For example, when a DLsubframe is followed immediately by an UL subframe, the DL subframe maybe partially erased in the UE receiver, which the eNB may consider inthe DL modulation and coding scheme (MCS) selection. To facilitate theproper MCS back-off, the information required by the eNB generallyincludes the UE switch time (e.g., should have standardized performancerequirements), UL-DL timing advance, and the UE capability to nulllog-likelihood ratios (LLRs).

For the UL-DL timing advance, although the eNB issues time advancecommands, the eNB may not know the current time offset within the UE dueto the differential nature of timing adjustment updates. Therefore, itmay be useful to have a current timing advance information feedback fromthe UE to the eNB. Alternatively, the eNB may periodically request theUE to perform a PRACH procedure to establish the current timing advance.The eNB may estimate the timing advance from the reported UE powerheadroom (e.g., larger headroom may be a smaller timing advance),although this method may not be reliable. For some embodiments, the eNBmay make a worst case assumption based on knowing the eNB coverageradius.

For the UE capability to null LLRs, the UE may have a capability toconnect the receive power to transmit power offset and receive totransmit timing offset in order to determine the need of scaling down orzeroing the receive LLRs whenever it is known to the UE that the receivesignal is not reliable due to HD interference. There may be standardizedrequirements to ensure the UE has such capability. Due to the sparsenature of inserted DL reference signals, it may not be possible tomeasure the HD interference on a per OFDM symbol basis based onreference signal observations. The UE may be able to infer the level ofinterference based on a priori knowledge of signal timing and signalpower levels.

Embodiments of the present disclosure provide techniques for enablingcoexistence, in a given frequency band, of HD and FD terminals, byintroducing new frequency bands designated for HD operation andoverlapping existing frequency bands designated for FD operation. Unlessthe designation of the new HD frequency bands is universal (e.g.,world-wide) there may be problems in roaming cases where a givenfrequency band is designated as HD in some country/region and as FD insome other country/region. Therefore, it may be beneficial to add thenetwork capability to broadcast the HD support. As an example, a UE mayreceive a network indication in an FD band that indicates whether thereis support for HD operations. As a result, if the UE supports only HDoperations, the UE may be denied access and then perform networkacquisition operations with another base station that does support HDoperations.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in Figures, those operations maybe performed by any suitable corresponding counterpartmeans-plus-function components

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and Blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for wireless communications, comprising:determining an uplink transmission overlaps with a downlink transmissionin a subframe; and controlling transmissions with one or morehalf-duplex (HD) user equipments (UEs) such that only one of the uplinktransmission or the downlink transmission is performed in the subframewith one or more of the UEs.
 2. The method of claim 1, wherein thecontrolling comprises suspending another one of the uplink transmissionor the downlink transmission for transmission in a later subframe. 3.The method of claim 1, wherein the controlling comprises prioritizingthe uplink transmission or the downlink transmission over the other. 4.The method of claim 1, wherein the downlink transmission comprises apaging message indicating a system information change.
 5. The method ofclaim 1, wherein the uplink transmission comprises an uplink hybridautomatic retransmission request (HARQ) operation.
 6. The method ofclaim 1, wherein the determining comprises: comparing channel qualityindicator (CQI) report differences in channel state information (CSI)reporting subsets from the one or more HD UEs; and determiningincompatible downlink/uplink allocations between the one or more HD UEs.7. An apparatus for wireless communications, comprising: means fordetermining an uplink transmission overlaps with a downlink transmissionin a subframe; and means for controlling transmissions with one or morehalf-duplex (HD) user equipments (UEs) such that only one of the uplinktransmission or the downlink transmission is performed in the subframewith one or more of the UEs.
 8. The apparatus of claim 7, wherein themeans for controlling comprises means for suspending another one of theuplink transmission or the downlink transmission for transmission in alater subframe.
 9. The apparatus of claim 7, wherein the means forcontrolling comprises means for prioritizing the uplink transmission orthe downlink transmission over the other.
 10. The apparatus of claim 7,wherein the downlink transmission comprises a paging message indicatinga system information change.
 11. The apparatus of claim 7, wherein theuplink transmission comprises an uplink hybrid automatic retransmissionrequest (HARQ) operation.
 12. The apparatus of claim 7, wherein themeans for determining comprises: means for comparing channel qualityindicator (CQI) report differences in channel state information (CSI)reporting subsets from the one or more HD UEs; and means for determiningincompatible downlink/uplink allocations between the one or more HD UEs.13. An apparatus for wireless communications, comprising: at least oneprocessor configured to: determine an uplink transmission overlaps witha downlink transmission in a subframe; and control transmissions withone or more half-duplex (HD) user equipments (UEs) such that only one ofthe uplink transmission or the downlink transmission is performed in thesubframe with one or more of the UEs; and a memory coupled to the atleast one processor.
 14. The apparatus of claim 13, wherein the at leastone processor configured to control comprises suspending another one ofthe uplink transmission or the downlink transmission for transmission ina later subframe.
 15. The apparatus of claim 13, wherein the at leastone processor configured to control comprises prioritizing the uplinktransmission or the downlink transmission over the other.
 16. Theapparatus of claim 13, wherein the downlink transmission comprises apaging message indicating a system information change.
 17. The apparatusof claim 13, wherein the uplink transmission comprises an uplink hybridautomatic retransmission request (HARQ) operation.
 18. The apparatus ofclaim 13, wherein the at least one processor configured to determinecomprises: comparing channel quality indicator (CQI) report differencesin channel state information (CSI) reporting subsets from the one ormore HD UEs; and determining incompatible downlink/uplink allocationsbetween the one or more HD UEs.
 19. A computer-program product,comprising: a computer-readable medium having code for: determining anuplink transmission overlaps with a downlink transmission in a subframe;and controlling transmissions with one or more half-duplex (HD) userequipments (UEs) such that only one of the uplink transmission or thedownlink transmission is performed in the subframe with one or more ofthe UEs.
 20. The computer-program product of claim 19, wherein the codefor controlling comprises code for suspending another one of the uplinktransmission or the downlink transmission for transmission in a latersubframe.
 21. The computer-program product of claim 19, wherein the codefor controlling comprises code for prioritizing the uplink transmissionor the downlink transmission over the other.
 22. The computer-programproduct of claim 19, wherein the downlink transmission comprises apaging message indicating a system information change.
 23. Thecomputer-program product of claim 19, wherein the uplink transmissioncomprises an uplink hybrid automatic retransmission request (HARQ)operation.
 24. The computer-program product of claim 19, wherein thecode for determining comprises code for: comparing channel qualityindicator (CQI) report differences in channel state information (CSI)reporting subsets from the one or more HD UEs; and determiningincompatible downlink/uplink allocations between the one or more HD UEs.